Analysis of ocean color components within stratified and well‐mixed waters of the western English Channel

In situ pigment and dissolved organic carbon (DOC) data from two distinct hydrographic regions of the western English Channel are used to explore the possible marine DOC contamination of the past satellite estimates of phytoplankton biomass. To compare with field measurements, the individual spectral contributions of DOC, pigments, and water to the total diffuse attenuation coefficient, K par , are summed on a quantum basis within stratified waters near Plymouth, England; and for the spectrally averaged diffuse attenuation coefficient, K d , on an energy basis within tidally mixed waters near Roscofif, France. In addition, coastal zone color scanner (CZCS) images from 1979 to 1986 were used to compute DOC concentrations for comparison with in situ values. Our analysis suggests that almost 50% of the color signal of satellite‐sensed pigments may be attributed to absorption by marine colored DOC (CDOC) within the English Channel. These results compare favorably to the in situ DOC measurements off Plymouth, but not to off‐Roscoff measurements, suggesting that there may be more CDOC in the stratified waters and more nonabsorbing DOC in the tidally mixed waters.